According to the research, swimming is an exercise which causes fewer injuries for exercisers than jogging, cycling and ball games. Swimming increases cardiopulmonary function, muscle strength and metabolic rate of human bodies. In order to acquire the benefits mentioned above, people have to have enough swimming distance during the swimming process. However, the watercourse length of the swimming pool at home is limited by the size of the backyard and causing the inconvenience of the swim training.
U.S. Patent Application Publication No. 2004/0171270 discloses a swim training device. The swim training device includes a sensor and a restraint component. One end of the restraint component is fastened to a side of a water tank, and the other end of the restraint component is fastened to a swimmer. The sensor measures the force applied on the restraint component when the swimmer is swimming in the water tank. Therefore, this swimming training device helps the swimmer to do the swimming training in the water tank, and obtains a swimming speed of the swimmer by the processor according to the force measured by sensor. However, the accuracy of the swimming speed obtained by this swim training device is arguable.